Coverage enhancement level signaling and efficient packing of mtc system information

ABSTRACT

The present disclosure relates to transmitting and receiving of system information which includes controlling the transmission and/or the reception to transmit and/or receive system information including a coverage enhancement level indication for indicating enhanced coverage levels supported by the wireless communication system and to transmit and/or receive system information including a group of information elements common for different coverage enhancement levels and information elements specific for different coverage enhancement levels grouped for respective coverage enhancement levels.

BACKGROUND 1. Technical Field

The present disclosure relates to transmission and reception of systeminformation in a wireless communication system.

2. Description of the Related Art

Third-generation mobile systems (3G) based on WCDMA radio-accesstechnology are being deployed on a broad scale all around the world. Afirst step in enhancing or evolving this technology entails introducingHigh-Speed Downlink Packet Access (HSDPA) and an enhanced uplink, alsoreferred to as High Speed Uplink Packet Access (HSUPA), giving a radioaccess technology that is highly competitive.

In order to be prepared for further increasing user demands and to becompetitive against new radio access technologies, 3GPP introduced a newmobile communication system which is called Long Term Evolution (LTE).LTE is designed to meet the carrier needs for high speed data and mediatransport as well as high capacity voice support for the next decade.The ability to provide high bit rates is a key measure for LTE.

The work item (WI) specification on Long Term Evolution (LTE) calledEvolved UMTS Terrestrial Radio Access (UTRA) and UMTS Terrestrial RadioAccess Network (UTRAN) is finalized as Release 8 (LTE Rel. 8). The LTEsystem represents efficient packet-based radio access and radio accessnetworks that provide full IP-based functionalities with low latency andlow cost. In LTE, scalable multiple transmission bandwidths arespecified such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0 MHz, in order toachieve flexible system deployment using a given spectrum. In thedownlink, Orthogonal Frequency Division Multiplexing (OFDM) based radioaccess was adopted because of its inherent immunity to multipathinterference (MPI) due to a low symbol rate, the use of a cyclic prefix(CP) and its affinity to different transmission bandwidth arrangements.Single-carrier frequency division multiple access (SC-FDMA) based radioaccess was adopted in the uplink, since provisioning of wide areacoverage was prioritized over improvement in the peak data rateconsidering the restricted transmit power of the user equipment (UE).Many key packet radio access techniques are employed includingmultiple-input multiple-output (MIMO) channel transmission techniquesand a highly efficient control signaling structure is achieved in LTERel. 8/9.

The overall architecture is shown in FIG. 1 and a more detailedrepresentation of the E-UTRAN architecture is given in FIG. 2. TheE-UTRAN consists of an eNodeB, providing the E-UTRA user plane(PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towardsthe user equipment (UE). The eNodeB (eNB) hosts the Physical (PHY),Medium Access Control (MAC), Radio Link Control (RLC) and Packet DataControl Protocol (PDCP) layers that include the functionality ofuser-plane header-compression and encryption. It also offers RadioResource Control (RRC) functionality corresponding to the control plane.It performs many functions including radio resource management,admission control, scheduling, enforcement of negotiated uplink Qualityof Service (QoS), cell information broadcast, ciphering/deciphering ofuser and control plane data, and compression/decompression ofdownlink/uplink user plane packet headers. The eNodeBs areinterconnected with each other by means of the X2 interface.

The eNodeBs are also connected by means of the S1 interface to the EPC(Evolved Packet Core), more specifically to the MME (Mobility ManagementEntity) by means of the S1-MME and to the Serving Gateway (SGW) by meansof the S1-U. The S1 interface supports a many-to-many relation betweenMMES/Serving Gateways and eNodeBs. The SGW routes and forwards user datapackets, while also acting as the mobility anchor for the user planeduring inter-eNodeB handovers and as the anchor for mobility between LTEand other 3GPP technologies (terminating S4 interface and relaying thetraffic between 2G/3G systems and PDN GW). For idle state userequipments, the SGW terminates the downlink data path and triggerspaging when downlink data arrives for the user equipment. It manages andstores user equipment contexts, e.g. parameters of the IP bearerservice, network internal routing information. It also performsreplication of the user traffic in case of lawful interception.

The MME is the key control-node for the LTE access-network. It isresponsible for idle mode user equipment tracking and paging procedureincluding retransmissions. It is involved in the beareractivation/deactivation process and is also responsible for choosing theSGW for a user equipment at the initial attach and at time of intra-LTEhandover involving Core Network (CN) node relocation. It is responsiblefor authenticating the user (by interacting with the HSS). TheNon-Access Stratum (NAS) signaling terminates at the MME and it is alsoresponsible for generation and allocation of temporary identities touser equipments. It checks the authorization of the user equipment tocamp on the service provider's Public Land Mobile Network (PLMN) andenforces user equipment roaming restrictions. The MME is the terminationpoint in the network for ciphering/integrity protection for NASsignaling and handles the security key management. Lawful interceptionof signaling is also supported by the MME. The MME also provides thecontrol plane function for mobility between LTE and 2G/3G accessnetworks with the S3 interface terminating at the MME from the SGSN. TheMME also terminates the Sha interface towards the home HSS for roaminguser equipments.

FIG. 3 shows a radio frame structure for LTE FDD. The downlink componentcarrier of a 3GPP LTE (Release 8 and further) is subdivided in thetime-frequency domain in radio frames, which are further subdivided intoso-called subframes. In 3GPP LTE (Release 8 and further) each subframeis divided into two downlink slots, one of which is shown in FIG. 4. Thefirst downlink slot includes the control channel region (PDCCH region)within the first OFDM symbols. Each subframe consists of a given numberof OFDM symbols in the time domain (12 or 14 OFDM symbols in 3GPP LTE,Release 8 and further), wherein each OFDM symbol spans over the entirebandwidth of the component carrier. The OFDM symbols thus each consistsof a number of modulation symbols transmitted on respective N^(DL)_(RB)*N^(RB) _(SC) subcarriers. Assuming a multi-carrier communicationsystem, e.g. employing OFDM, as for example used in 3GPP Long TermEvolution (LTE), the smallest unit of resources that can be assigned bythe scheduler is one “resource block”. A physical resource block (PRB)is defined as N^(DL) _(symb) consecutive OFDM symbols in the time domain(e.g. 7 OFDM symbols) and N^(RB) _(SC) consecutive subcarriers in thefrequency domain as exemplified in FIG. 4 (e.g. 12 subcarriers for acomponent carrier). In 3GPP LTE (Release 8), a physical resource blockthus consists of N^(DL) _(symb)*N^(RB) _(SC) resource elements,corresponding to one slot in the time domain and 180 kHz in thefrequency domain (for further details on the downlink resource grid, seefor example 3GPP TS 36.211, “Evolved Universal Terrestrial Radio Access(E-UTRA); Physical Channels and Modulation (Release 8)”, version 8.9.0,section 6.2, available at http://www.3gpp.org and incorporated herein byreference).

One subframe consists of two slots, so that there are 14 OFDM symbols ina subframe when a so-called “normal” CP (cyclic prefix) is used, and 12OFDM symbols in a subframe when a so-called “extended” CP is used. Forsake of terminology, in the following the time-frequency resourcesequivalent to the same N^(RB) _(SC) consecutive subcarriers spanning afull subframe is called a “resource block pair”, or equivalent “RB pair”or “PRB pair”.

The term “component carrier” refers to a combination of several resourceblocks in the frequency domain. In future releases of LTE, the term“component carrier” is no longer used; instead, the terminology ischanged to “cell”, which refers to a combination of downlink andoptionally uplink resources. The linking between the carrier frequencyof the downlink resources and the carrier frequency of the uplinkresources is indicated in the system information transmitted on thedownlink resources.

Similar assumptions for the component carrier structure apply to laterreleases too.

Downlink control information occurs in several formats that differ inoverall size and also in the information contained in its fields. Thedifferent DCI formats that are currently defined for LTE are as followsand described in detail in 3GPP TS 36.212, “Multiplexing and channelcoding”, version 12.4.0, section 5.3.3.1 (available athttp://www.3gpp.org and incorporated herein by reference). For furtherinformation regarding the DCI formats and the particular informationthat is transmitted in the DCI, please refer to the technical standardor to LTE—The UMTS Long Term Evolution—From Theory to Practice, Editedby Stefanie Sesia, Issam Toufik, Matthew Baker, Chapter 9.3,incorporated herein by reference.

In order that the UE can identify whether it has received a PDCCHtransmission correctly, error detection is provided by means of a 16-bitCRC appended to each PDCCH (i.e. DCI). Furthermore, it is necessary thatthe UE can identify which PDCCH(s) are intended for it. This could intheory be achieved by adding an identifier to the PDCCH payload;however, it turns out to be more efficient to scramble the CRC with the“UE identity”, which saves the additional overhead. The CRC may becalculated and scrambled as defined in detail by 3GPP in TS 36.212,Section 5.3.3.2 “CRC attachment”, incorporated hereby by reference. Thesection describes how error detection is provided on DCI transmissionsthrough a Cyclic Redundancy Check (CRC). A brief summary is given below.The entire payload is used to calculate the CRC parity bits. The paritybits are computed and attached. In the case where UE transmit antennaselection is not configured or applicable, after attachment, the CRCparity bits are scrambled with the corresponding RNTI.

The scrambling may further depend on the UE transmit antenna selection,as apparent from TS 36.212. In the case where UE transmit antennaselection is configured and applicable, after attachment, the CRC paritybits are scrambled with an antenna selection mask and the correspondingRNTI. As in both cases the RNTI is involved in the scrambling operation,for simplicity and without loss of generality the following descriptionof the embodiments simply refers to the CRC being scrambled (anddescrambled, as applicable) with an RNTI, which should therefore beunderstood as notwithstanding e.g. a further element in the scramblingprocess such as an antenna selection mask.

Correspondingly, the UE descrambles the CRC by applying the “UEidentity” and, if no CRC error is detected, the UE determines that PDCCHcarries its control information intended for itself. The terminology of“masking” and “de-masking” is used as well, for the above-describedprocess of scrambling a CRC with an identity.

The “UE identity” mentioned above with which the CRC of the DCI may bescrambled can also be a SI-RNTI (System Information Radio NetworkTemporary Identifier), which is not a “UE identity” as such, but ratheran identifier associated with the type of information that is indicatedand transmitted, in this case the system information. The SI-RNTI isusually fixed in the specification and thus known as priority to allUEs.

There are various types of RNTIs that are used for different purposes.The following table taken from 3GPP 36.321, “Evolved UniversalTerrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocolspecification”, version 12.5.0, Chapter 7.1 shall give an overview ofthe various 16-bits RNTIs and their usages.

TABLE 1 Value (hexa-decimal) RNTI 0000 N/A 0001-003C RA-RNTI, C-RNTI,Semi-Persistent Scheduling C-RNTI, Temporary C-RNTI, TPC-PUCCH-RNTI andTPC-PUSCH-RNTI (see note) 003D-FFF3 C-RNTI, Semi-Persistent SchedulingC-RNTI, Temporary C-RNTI, TPC-PUCCH-RNTI and TPC-PUSCH-RNTI FFF4-FFFCReserved for future use FFFD M-RNTI FFFE P-RNTI FFFF SI-RNTI

Physical Downlink Control Channel (PDCCH) and Physical Downlink SharedChannel (PDSCH)

The physical downlink control channel (PDCCH) carries e.g. schedulinggrants for allocating resources for downlink or uplink datatransmission. Multiple PDCCHs can be transmitted in a subframe.

The PDCCH for the user equipments is transmitted on the first N^(PDCCH)_(symb) OFDM symbols (usually either 1, 2 or 3 OFDM symbols as indicatedby the PCFICH, in exceptional cases either 2, 3, or 4 OFDM symbols asindicated by the PCFICH) within a subframe, extending over the entiresystem bandwidth; the system bandwidth is typically equivalent to thespan of a cell or component carrier. The region occupied by the firstN^(PDCCH) _(symb) OFDM symbols in the time domain and the N^(DL)_(RB)*N^(RB) _(SC) subcarriers in the frequency domain is also referredto as PDCCH region or control channel region. The remaining N^(PDSCH)_(symb)=2*N^(DL) _(symb)−N^(PDCCH) _(symb) OFDM symbols in the timedomain on the N^(DL) _(RB)*N^(RB) _(SC) subcarriers in the frequencydomain is referred to as the PDSCH region or shared channel region (seebelow).

For a downlink grant (i.e. resource assignment) on the physical downlinkshared channel (PDSCH), the PDCCH assigns a PDSCH resource for (user)data within the same subframe. The PDCCH control channel region within asubframe consists of a set of CCE where the total number of CCEs in thecontrol region of subframe is distributed throughout time and frequencycontrol resource. Multiple CCEs can be combined to effectively reducethe coding rate of the control channel. CCEs are combined in apredetermined manner using a tree structure to achieve different codingrate.

On a transport channel level, the information transmitted via the PDCCHis also referred to as L1/L2 control signaling (for details on L1/L2control signaling see above).

A common technique for error detection and correction in packettransmission systems over unreliable channels is called hybrid AutomaticRepeat request (HARM). Hybrid ARQ is a combination of Forward ErrorCorrection (FEC) and ARQ.

If a FEC encoded packet is transmitted and the receiver fails to decodethe packet correctly (errors are usually checked by a CRC (CyclicRedundancy Check)), the receiver requests a retransmission of thepacket. Generally (and throughout this document) the transmission ofadditional information is called “retransmission (of a packet)”,although this retransmission does not necessarily mean a transmission ofthe same encoded information, but could also mean the transmission ofany information belonging to the packet (e.g. additional redundancyinformation).

Depending on the information (generally code-bits/symbols), of which thetransmission is composed, and depending on how the receiver processesthe information, the following Hybrid ARQ schemes are defined.

In Type I HARQ schemes, the information of the encoded packet isdiscarded and a retransmission is requested, if the receiver fails todecode a packet correctly. This implies that all transmissions aredecoded separately. Generally, retransmissions contain identicalinformation (code-bits/symbols) to the initial transmission.

In Type II HARQ schemes, a retransmission is requested, if the receiverfails to decode a packet correctly, where the receiver stores theinformation of the (erroneously received) encoded packet as softinformation (soft-bits/symbols). This implies that a soft-buffer isrequired at the receiver. Retransmissions can be composed out ofidentical, partly identical or non-identical information(code-bits/symbols) according to the same packet as earliertransmissions. When receiving a retransmission the receiver combines thestored information from the soft-buffer and the currently receivedinformation and tries to decode the packet based on the combinedinformation. (The receiver can also try to decode the transmissionindividually, however generally performance increases when combiningtransmissions.) The combining of transmissions refers to so-calledsoft-combining, where multiple received code-bits/symbols are likelihoodcombined and solely received code-bits/symbols are code combined. Commonmethods for soft-combining are Maximum Ratio Combining (MRC) of receivedmodulation symbols and log-likelihood-ratio (LLR) combining (LLR combingonly works for code-bits).

Type II schemes are more sophisticated than Type I schemes, since theprobability for correct reception of a packet increases with everyreceived retransmission. This increase comes at the cost of a requiredhybrid ARQ soft-buffer at the receiver. This scheme can be used toperform dynamic link adaptation by controlling the amount of informationto be retransmitted. E.g. if the receiver detects that decoding has been“almost” successful, it can request only a small piece of informationfor the next retransmission (smaller number of code-bits/symbols than inprevious transmission) to be transmitted. In this case it might happenthat it is even theoretically not possible to decode the packetcorrectly by only considering this retransmission by itself(non-self-decodable retransmissions).

Type III HARQ schemes may be considered a subset of Type II schemes: Inaddition to the requirements of a Type II scheme each transmission in aType III scheme must be self-decodable.

Synchronous HARQ means that the re-transmissions of HARQ blocks occur atpredefined periodic intervals. Hence, no explicit signaling is requiredto indicate to the receiver the retransmission schedule.

Asynchronous HARQ offers the flexibility of scheduling re-transmissionsbased on air interface conditions. In this case some identification ofthe HARQ process needs to be signaled in order to allow for a correctcombining and protocol operation. In 3GPP LTE systems, HARQ operationswith eight processes are used. The HARQ protocol operation for downlinkdata transmission will be similar or even identical to HSDPA.

In uplink HARQ protocol operation there are two different options on howto schedule a retransmission. Retransmissions are either “scheduled” bya NACK (also referred to as a synchronous non-adaptive retransmission)or are explicitly scheduled by the network by transmitting a PDCCH (alsoreferred to as synchronous adaptive retransmissions). In case of asynchronous non-adaptive retransmission the retransmission will use thesame parameters as the previous uplink transmission, i.e. theretransmission will be signaled on the same physical channel resources,respectively uses the same modulation scheme/transport format.

Since synchronous adaptive retransmissions are explicitly scheduled viaPDCCH, the eNodeB has the possibility to change certain parameters forthe retransmission. A retransmission could be for example scheduled on adifferent frequency resource in order to avoid fragmentation in theuplink, or eNodeB could change the modulation scheme or alternativelyindicate to the user equipment what redundancy version to use for theretransmission. It should be noted that the HARQ feedback (ACK/NACK) andPDCCH signaling occurs at the same timing. Therefore the user equipmentonly needs to check once whether a synchronous non-adaptiveretransmission is triggered (i.e. only a NACK is received) or whethereNode B requests a synchronous adaptive retransmission (i.e. PDCCH issignaled).

The reception of system information (SI) is an operation to be performedby a UE on the basis of a scanned RF signal and a detectedsynchronization signal. In particular, upon the detection ofsynchronization signals the UE is capable of identifying a cell and ofsynchronizing with downlink transmissions by the cell. Accordingly, theUE may receive a broadcast channel, BCH, of a cell, and, hence, thecorresponding system information. On the basis thereof, the UE candetect whether or not a cell is suitable for selection and/orreselection, i.e. whether the cell is a candidate cell.

System information is information which is transmitted in a broadcastmanner to all UEs in a cell. It includes information necessary for cellselection and some parts thereof are to be read at any cellselection/reselection, after the UE synchronizes with the cell.

System information is structured by means of System Information Blocks(SIBs), each of which includes a set of parameters. In particular,system information is transmitted in a Master Information Block, MIB,and a number of System Information Blocks. The MIB includes a limitednumber of the most essential and most frequently transmitted parametersthat are needed to acquire other information from the cell such as thedownlink system bandwidth, an indicator of the resources allocated toHARQ acknowledgement signaling in the downlink, and the System FrameNumber (SFN). The remaining SIBs are numbered; there are SIBs 1 to 13defined in Release 8.

SIB1 contains parameters needed to determine if a cell is suitable forcell selection, as well as information about the time domain schedulingof the other SIBs. SIB2 includes common and shared channel information.SIBs 3 to 8 include parameters used to control intra-frequency,inter-frequency and inter-Radio Access Technology (RAT) cellreselection. SIB9 is used to signal the name of a Home eNodeB, whereasSIBs 10 to 12 include the Earthquake and Tsunami Warning Service (ETWS)notifications and Commercial Mobile Alert System (CMAS) warningmessages. Finally, SIB 13 includes MBMS related control information.

The system information is transmitted by the RRC protocol in three typesof messages: the MIB message, the SIB1 message and SI message. The MIBmessages are carried on the Physical Broadcast Channel (PBCH) whereasthe remaining SIB1 and SI messages are at the physical layer multiplexedwith unicast data transmitted on the Physical Downlink Shared Channel(PDSCH).

The MIB is transmitted at a fixed cycles. The SIB1 is also transmittedat the fixed cycles. In order to improve robustness of the systeminformation transmission, the system information is repeated. Therepetitions have different redundancy versions and thus, they are notrepetitions of the bits effectively transmitted but rather repetitionsof the data carried but coded differently. For instance, MIB istransmitted every frame in the first subframe (subframe #0) wherein thenew MIB (MIB with content possibly different from the previous MIBs) istransmitted every four frames and the remaining three frames carry itsrepetition. Similarly, repetition coding is applied for transmission ofSIB 1. A new SIB1 is transmitted every 8 frames. Each SIB1 has threefurther repetitions. All other SIBs are being transmitted at the cyclesspecified by SIB scheduling information elements in SIB 1. Inparticular, the mapping of SIBs to a SI message is flexibly configurableby schedulingInfoList included in SIB1, with restrictions that each SIBis contained only in a single SI message, and at most once in thatmessage. Only SIBs having the same scheduling requirement (periodicity)can be mapped to the same SI message; SIB2 is always mapped to the SImessage that corresponds to the first entry in the list of SI messagesin the schedulingInfoList. There may be multiple SI messages transmittedwith the same periodicity.

Thus, a terminal determines the SI widow based on the signaledinformation and starts receiving (blind decoding) of the downlink sharedchannel using the SI-RNTI (an identifier meaning that signalinginformation is transmitted) from the start of the SI window and continuefor each subframe until the end of the SI-window or until the SI messagewas received, excluding the subframe #5 in radio frames for which SFNmod 2=0, any MBSFN subframes, and any uplink subframes in TDD. If the SImessage was not received by the end of the SI-window, the reception isrepeated at the next SI-window occasion for the concerned SI message.

In other words, during blind decoding, the UE tries to decode PDCCH oneach subframe of an SI-window the SI-RNTI but only some of thesesubframes really carry PDCCH (CRC) encoded using the SI-RNTI(corresponding to PDSCH containing the particular SI).

For further details on the definition of system information, see forexample 3GPP, TS 36.331, V12.5.0, “3rd Generation Partnership Project;Technical Specification Group Radio Access Network; Evolved UniversalTerrestrial Radio Access (E-UTRA); Radio Resource Control (RRC);Protocol specification (Release 12)”, sections 6.2.2.7 and 6.3.1,available at http://www.3gpp.org and incorporated herein by reference.

As LTE deployments evolve, operators strive to reduce the cost ofoverall network maintenance by minimizing the number of RATs. In thisrespect, Machine-Type Communications (MTC) devices is a market that islikely to continue expanding in the future.

Many MTC devices are targeting low-end (low cost, low data rate)applications that can be handled adequately by GSM/GPRS. Owing to thelow cost of these devices and good coverage of GSM/GPRS, there is verylittle motivation for MTC device suppliers to use modules supporting theLTE radio interface.

As more and more MTC devices are deployed in the field, this naturallyincreases the reliance on GSM/GPRS networks. This will cost operatorsnot only in terms of maintaining multiple RATs, but also preventoperators reaping the maximum benefit out of their spectrum (given thenon-optimal spectrum efficiency of GSM/GPRS). With users and trafficbecoming denser, using more spectral-efficient technologies, such asLong Term Evolution (LTE), allow the operators to utilize their spectrumin a much more efficient way.

Given the likely high number of MTC devices, the overall resource theywill need for service provision may be correspondingly significant, andinefficiently assigned (for further details on objectives for MTC, seefor example 3GPP, RP-150492 Ericsson: “Revised WI: Further LTE PhysicalLayer Enhancements for MTC”, section 4, available at http://www.3gpp.organd incorporated herein by reference).

Approaches to lower the cost of LTE presently regard the volume ofproducts as the primary reason. The impact of volume can be seen in twopossible ways, depending on how low-cost MTC is developed. Firstly, iflow-cost MTC may be very similar to mainline LTE and included in LTEchipsets, MTC has the benefit of the volume of LTE. Secondly, a low-costMTC based on LTE may have significantly lower cost than mainline LTE.Although it appears not to have the volume benefit of LTE, the volume ofMTC devices can be even larger due to a potentially greater number ofsupported MTC applications and scenarios.

In this respect, the following approaches to lower the cost of LTE, i.e.defining low-cost MTC are discussed and found to have significant UEcost impact (for further details on low-cost MTC devices, see forexample 3GPP, R1-112912, Huawei, HiSilicon, CMCC: “Overview on low-costMTC UEs based on LTE”, section 4, available at http://www.3gpp.org andincorporated herein by reference):

-   -   Reduction in supported bandwidth for the low-cost LTE: The low        cost of 1.4 MHz (6 RB) downlink bandwidth could cover most        application scenarios of MTC. However, 3 MHz (15 RB) or 5 MHz        (25 RB) could be considered given that the complexity does not        increase much. Given that the uplink may have a larger        requirement for MTC services, the possibility of reduced        transmit power, and small baseband complexity (relative to        downlink reception), any reduction in minimum transmission        bandwidth in the UE should be carefully justified.    -   Modified PDCCH-related design for the low-cost LTE to simplify        the PDCCH blind decoding and give efficient channel access for a        large number of MTC devices. A reduction in maximum bandwidth        (e.g., 1.4 MHz) decreases PDCCH blind decoding naturally.    -   Protocol simplification including HARQ consideration, MAC, RLC        and RRC protocol. Signaling reduction between low duty cycle MTC        devices and the base station.    -   Transmission modes down-selection to maintain coverage and        balance complexity.

Further considerations on low-cost MTC devices relate to an improvedindoor coverage. A number of applications require indoor deployment ofMachine Type Communication, MTC, devices, e.g. in an apartment basement,or on indoor equipment that may be close to the ground floor etc. TheseUEs would experience significantly greater penetration losses on theradio interface than normal LTE devices. This effectively means thatindoor coverage should be readily available and reliable: i.e. shouldprovide a significant improvement on existing coverage.

Additionally, regarding the power consumption of low-cost MTC devices itis noted that many applications require devices to have up to ten yearsof battery life. In this respect, presently available Power Save Modesappear not sufficient to achieve the envisaged battery life. In thisrespect, it is anticipated that further techniques are proposed tosignificantly cut down the power usage of MTC devices e.g. by optimizingsignaling exchanges in the system, in order to realize battery life ofup to ten years.

For improving indoor coverage (for low-cost MTC devices), recentdevelopments have focused on an Enhanced Coverage, EC, mode that isapplicable to UEs e.g. operating delay tolerant MTC applications.Another term is “Coverage Extension”. The corresponding Work Item in3GPP Release 12 “Low cost & enhanced coverage MTC UE for LTE” came tothe conclusion that further complexity reduction of LTE devices for MTCcan be achieved if additional complexity reduction techniques aresupported, as apparent from the technical report TR 36.888, v12.0.0,“Machine-Type Communications (MTC) User Equipments (UEs)”, available atwww.3gpp.org and incorporated herein by reference. The technical reportTR 36.888 concluded that a coverage improvement target of 15-20 dB forboth FDD and TDD in comparison to a normal LTE footprint could beachieved to support the use cases where MTC devices are deployed inchallenging locations, e.g. deep inside buildings, and to compensate forgain loss caused by complexity-reduction techniques. MTC coverageenhancements are now expected to be introduced in 3GPP Release 13.

In general, the MTC devices may be low complexity (LC) MTC devices(which basically forces the device to receive a TBS of 1000 bits or lessas a result of buffer size limitations and other implementationlimitations) or enhanced coverage (EC) devices which are supposed tosupport a large number of repetitions.

In other words, LC are Low Complexity devices which are meant to beinexpensive devices with limited buffer sizes/simple implementation etc.whereas the EC devices are the coverage enhanced device that shouldoperate in challenging situations like in basement or far away from thecell center.

The general objective is to specify a new UE for MTC operation in LTEthat allows for enhanced coverage and lower power consumption. Some ofthe additional objectives are given below:

-   -   Reduced UE bandwidth of 1.4 MHz in downlink and uplink.    -   Bandwidth reduced UEs should be able to operate within any        system bandwidth.    -   Frequency multiplexing of bandwidth reduced UEs and non-MTC UEs        should be supported.    -   The UE only needs to support 1.4 MHz RF bandwidth in downlink        and uplink.    -   The allowed re-tuning time supported by specification (e.g. ˜0        ms, 1 ms) should be determined by RAN4.    -   Reduced maximum transmit power.    -   The maximum transmit power of the new UE power class should be        determined by RAN4 and should support an integrated PA        implementation.    -   Reduced support for downlink transmission modes.

The following further UE processing relaxations can also be consideredwithin this work item:

-   -   Reduced maximum transport block size for unicast and/or        broadcast signaling.    -   Reduced support for simultaneous reception of multiple        transmissions.    -   Relaxed transmit and/or receive EVM requirement including        restricted modulation scheme. Reduced physical control channel        processing (e.g. reduced number of blind decoding attempts).    -   Reduced physical data channel processing (e.g. relaxed downlink        HARQ time line or reduced number of HARQ processes).    -   Reduced support for CQI/CSI reporting modes.    -   A relative LTE coverage improvement—corresponding to 15 dB for        FDD—for the UE category/type defined above and other UEs        operating delay-tolerant MTC applications with respect to their        respective normal coverage shall be possible. At least some of        the following techniques, which shall be applicable for both FDD        and TDD, can be considered to achieve this:    -   Subframe bundling techniques with HARQ for physical data        channels (e.g. PDSCH, PUSCH)    -   Elimination of use of control channels (e.g. PCFICH, PDCCH)    -   Repetition techniques for control channels (e.g. PBCH, PRACH,        (E)PDCCH)    -   Either elimination or repetition techniques (e.g. PBCH, PHICH,        PUCCH)    -   Uplink PSD boosting with smaller granularity than 1 PRB    -   Resource allocation using EPDCCH with cross-subframe scheduling        and repetition (EPDCCH-less operation can also be considered)    -   New physical channel formats with repetition for SIB/RAR/Paging    -   A new SIB for bandwidth reduced and/or coverage enhanced UEs    -   Increased reference symbol density and frequency hopping        techniques    -   Relaxed “probability of missed detection” for PRACH and initial        UE system acquisition time for PSS/SSS/PBCH/SIBs can be        considered as long as the UE power consumption impact can be        kept on a reasonable level.    -   Spreading: Spreading refers to spreading of information across        resources including time-frequency domain resources or even        spreading using Scrambling (or Channelization) codes.

There can be also other techniques than those listed above. The amountof coverage enhancement should be configurable per cell and/or per UEand/or per channel and/or group of channels, such that different levelsof coverage enhancements exist. The different levels of coverageenhancement could mean different level of CE techniques being applied tosupport the CE-device transmission and reception. Relevant UEmeasurements and reporting to support this functionality should bedefined.

For more details, see for example 3GPP RP-141865 “Revised WI: FurtherLTE Physical Layer Enhancements for MTC” sourced by Ericsson, availableat http://www.3gpp.org and incorporated herein by reference.

Notably, coverage enhancements of 15/20 dB for UEs in the EnhancedCoverage mode with respect to their nominal coverage means that the UEshave to be capable of receiving extremely low signal strengths. Thisapplies not only to the initial scanning operation, the cell search andthe cell selection operation but also the subsequent communicationscheme to be performed by the UE. As described above, there will bedifferent levels of CE depending on the network support and UEcapability, e.g. 5/10/15 dB coverage extension.

Early attempts to define the Enhanced Coverage mode have focused onmodifications of the radio transmissions. In this respect, discussionshave focused on repeated transmissions as being the main technique toimprove the coverage. Repetitions can be applied to every channel forcoverage improvement.

An exemplary implementation of these repeated transmissions prescribesthat the same data is transmitted across multiple sub-frames. Yet, itwill become immediately apparent that these repeated transmissions willuse more resources (time-frequency) than what is required for normalcoverage UEs. RANI indicated that the transport block size used fortransmission to the MTC devices will be less than 1000 bits.

In view of the above requirements, a new information message schedulingwill be necessary to minimize the system overheard as well as not toaffect the system of previous releases and legacy UEs served thereby.

SUMMARY

One non-limiting and exemplary embodiment provides apparatuses andmethods for an efficient transmission and reception of systeminformation in a wireless network.

In one general aspect, the techniques disclosed here feature anapparatus for receiving system information in a wireless communicationsystem supporting coverage enhancement, including: a receiver thatreceives system information; and a controller that controls the receiverto receive system information including a coverage enhancement levelindication for indicating enhanced coverage levels supported by thewireless communication system, and to receive system informationincluding a group of information elements common for different coverageenhancement levels and one or more groups of information elementsspecific for different coverage enhancement levels.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

The above and other features of the present disclosure will become moreapparent from the following description and preferred embodiments givenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a current 3GPP architecture formachine-type communication;

FIG. 2 is a block diagram illustrating an exemplary architecture of aradio access network in 3GPP LTE;

FIG. 3 is a schematic diagram illustrating the general structure of aframe in 3GPP LTE FDD;

FIG. 4 is a schematic diagram illustrating the general structure of asub-frame on a downlink component carrier defined for 3GPP LTE;

FIG. 5 is a schematic diagram illustrating grouping of informationelements of system information into system information blocks fordifferent CE levels;

FIG. 6 is a schematic diagram illustrating an exemplary systeminformation block structure for different CE levels;

FIG. 7 is a schematic diagram illustrating comparison between the legacysystem information signaling and signaling of system information forMTC;

FIG. 8 is a block diagram illustrating a receiving and a transmittingapparatus;

FIG. 9 is a flowchart illustrating a receiving and transmitting method;and

FIG. 10 is a schematic diagram illustrating interleaving of transmissionof different SIB/SI.

DETAILED DESCRIPTION

The present disclosure relates to transmission and reception of systeminformation in a wireless communication system which is particularlysuitable for transmission and reception of system information formachine type communication such as the MTC in the 3GPP LTE. The systeminformation signaling has been recently discussed in 3GPP and thefollowing aims have been preliminarily agreed on:

-   -   maintain the flexibility similar to the one offered by the        current SIB concept, i.e., the size of the SIBs should not be        fixed.    -   branch from SIB1, i.e., LC/EC UEs receive a separate occurrence        of SIB1 and others (different time/frequency resources). The new        SIB1 is common for EC and LC.    -   transmit SIB1 information separately from other SIBs (in        particular to low cost UEs in normal coverage), if feasible in        terms of overhead and total acquisition time.    -   the scheduling information (time, frequency and MCS/TBS)        allowing acquiring SIB1 for LC/EC UEs could e.g. be carried in        MIB, i.e., dynamic L1 information in PDCCH is not needed.    -   SIB1 for LC/EC UEs could contain scheduling information (time,        frequency and MCS/TBS) allowing acquiring subsequent SIBs        without reading PDCCH.    -   the TB size restriction of 1000 bit for broadcast may be        acceptable, assuming that the network provides separate SIBs        (different time/frequency resources) to LC/EC UEs and legacy        UEs.

If the current mechanism for transmission of system information isapplied for communication applying a large number of repetitions such asMTC communication, each of the SIBs currently used will be transmittedwith approximately 50 times higher repetition rate. In general, therepetition rates may be also higher such as more than 200 repetitions.The number of repetitions may also be variable (configurable).

These would affect, for instance:

-   -   the acquisition time for the system information by the legacy        UEs if the system information blocks do not overlap and thus,        repetition of the system information would cause longer        transmission delay of the system information block and therefore        also increased the delay of the transmission of the next system        information block,    -   repeated transmissions of the entire system information would        also lead to a huge system load, which may be unnecessary since        the MTC devices does not make use of all information transmitted        in the current system information signaling. Accordingly, the        MTC UEs would receive irrelevant system information.    -   The reception of the entire system information that would        increase power consumption in the MTC device.

It is beneficial to provide several possible levels of coverageenhancement. However, any additional overhead which may result fromadditional signaling concerning different coverage enhancement levelsmay be critical especially in view of the high number of repetitionsthat may be necessary for some of the coverage enhancement levels inorder to convey the information. Accordingly, it is beneficial toprovide an efficient signaling concerning the support of multiplecoverage enhancement levels.

Advantageously, a cell indicates, which CE level(s) it does support.This indication may be broadcasted in the cell within the systeminformation so that the terminals are able to receive the informationand decide whether to apply the corresponding CE level operation.

For instance, the CE levels supported may be transmitted within thesystem information and in particular within the master information block(MIB) which is broadcasted on a physical layer. In the LTE, the MIB istransmitted via physical broadcast channel which can be received anddecoded by any terminal. However, the present disclosure is not limitedthereto and the broadcast may be performed over downlink shared channel.For instance, the CE levels may be indicated within SIB 1. Stillalternatively, the CE levels may be transmitted in another SIB, thelocation of which is either scheduled (for instance in the MIB or SIB1or another specific SIB) order to remind by blind decoding applyingSI-RNTI or an RNTI specific for MTC operation.

From the above possibilities, transmitting the CE levels within the MIBhas the advantage that the information on the CE levels is immediatelyavailable to the terminals via physical broadcasting. This increases theprobability and decreases delay of acquisition of the CE levels. On theother hand, generically the information signaled within the MIB shouldbe minimized in order to use the resources efficiently and to avoid theterminals read broadcast information which is not necessarily importantfor them. On the other hand, signaling the CE levels in SIB1 providesthe advantage that no further blind detection using SI-RNTI or othergroup RNTI is necessary to find other SIBs. This is beneficialespecially for MTC terminals which may suffer from bad channelconditions (being located on the border of the coverage in the cell) orwhich have technically simple implementation and are supposed topossibly efficiently use the power. Still alternatively are directlyscheduled SIB other than MIB or SIB1 may be used for signaling the CElevels.

Different levels of CE applicable for communication between the UE andthe network depend on the network support and on the UE capability. Forinstance, 5, 10, or 15 dB (or even more) coverage extension may besupported and denoted as respective low, medium, and high CE levels. Anormal coverage may be referred to as zero (0 dB) coverage extension,i.e. no extension.

Certain information elements (IEs) carrying parameters of the systeminformation may have the same value for different CE levels, whereasother IEs are to have different/unique values among the differentlevels. For instance, some examples of common value SIBs are typicallySIBs like ETWS/CMAS as briefly described above, and IEs such asdifferent neighbor lists (intra-freq, inter freq, inter RAT etc.) andACB, Access Class Barring, (cell level). Some examples ofdifferent/unique values among the different levels of CE are Cell (Re)Selection parameters (like q-RxLevMin, q-RxQualMin etc.), PRACHparameters and some others in RadioResourceConfigCommon SIB3, EAB(SIB14) etc.

For instance, possible typical values of qRxLevMin (in dBm) specified inSIB for sale detection/reselection for respective different CE levelsare exemplified below:

q-RxLevMin_zero −60 q-RxLevMin_low −50 q-RxLevMin_med −40q-RxLevMin_high −30

According to an embodiment of the present disclosure, there is providedefficient signaling and packing of system information which may becommon as well as different for different CE levels.

Signaling together system information related to all CE levels may leadto severe cell overload. On the other hand, separate signaling for eachCE level may complicate the eNB scheduler and UE behavior in acquiringand re-acquiring of the system information upon change of levels andupon SI change notifications.

One possible approach is to pack all information irrespective of the CElevels together, structured as in legacy case, i.e. no coverageenhancement. In this approach, when needed, an IE will have exactly asmany values as the number of CE levels supported, i.e. one per CE level.However, since the CE specific techniques like repetition number may bedifferent for each CE level, the above approach might lead tounnecessary system load as illustrated in the following calculation. Letus assume that the number of repetitions applied to each data block forzero, low, med, high CE levels is respectively 4, 10, 20, 50 repetitionsand the size of a legacy SIBx is 100 (bits).

If separate SIBs are transmitted for each CE level, the respectivenumber of bits necessary will be 4*100, 10*100, 20*100, and 50*100resulting in the total overhead of 400+1000+2000+5000=8400 bits. If onthe other hand, the information elements for all CE levels are parked inthe same system information block, this blog has to be repeated maximumnumber of time, i.e. 50 times, resulting in total overhead of50*400=20000 bits. If a compromise solution is chosen and to systeminformation blocks are used, each for two CE levels, the total overheadamounts to 10*200 and 50*200, resulting in 2000+10000=12000 bits.

As can be seen from the above examples, the structuring and grouping ofthe information concerning the different coverage enhancement levels hasa high impact on overhead transmitted and thus also to the transmissionefficiency.

As discussed above, it is beneficial to provide the CE levels supportedin the cell by means of the cell broadcast. The CE level indication mayhave different formats. For instance, the CE levels supported may beexplicitly signaled (e.g. in SIB1 or MIB or in another way as mentionedabove) for instance by listing them.

However, in order to save some signaling bits, only the highestsupported CE level may be signaled explicitly. A device receiving suchindications signaling the highest supported CE level then assumes thatall lower CE levels are also supported.

Still alternatively, the CE levels may be indicated indirectly, forinstance, by broadcasting as many values of a particular parameter (e.g.related to Cell Selection or Cell Reselection parameters likeq-RxLevMin) as there are the supported CE levels. In order to make themapping unambiguous, the values are ordered in a predefined manner, forinstance starting with the specified highest CE level and coming down tothe lower levels or starting with the specified lowest CE level andgoing up to the higher levels or any other way.

In order to efficiently signal information elements for different CElevels, according to an exemplary embodiment, all IEs with differentcontent (value) for different CE levels are grouped per CE level. Forinstance, there is one SIB per CE level. The remaining IEs which havethe same content (values) for all CE levels are grouped together inanother one SIB common for all CE levels. This approach is illustratedin FIG. 5.

FIG. 5 illustrates in the upper part transmission of informationelements which have different content for different respective CElevels. The term “content” here refers to the values of particularparameters. The values do not have to be effectively always different.Rather what is meant is that they may be set to different values fordifferent respective CE levels. As explained above, the values fordifferent CE levels are advantageously transmitted with different numberof repetitions. In this example, correspondingly, the values fordifferent CE levels are also transmitted with different periodicity.

In the different content case shown in the upper part of FIG. 5, thereare two different SI/SIB transmissions (cf. solid line and dashed line,respectively). The content illustrated by a solid line 510 hererepresents higher CE levels and is therefore transmitted more frequentlythan the content illustrated by the dashed line 520 which representslower CE levels.

In FIG. 5, “P1” denotes the first periodicity (frequency) oftransmitting system information for the first CE level which is higherthan the second periodicity (frequency) denoted as “P2” for transmittingSI concerning the second CE level lower than the first CE level. It isassumed that lower CE level means smaller coverage enhancement whereas ahigher CE level means larger coverage enhancement (reception possiblealso at lower signal strength than for the lower CE levels).

The bottom part of FIG. 5 illustrates transmission of informationelements which have common content for different respective CE levels(levels of 5 dB, 10 dB and 15 dB corresponding to “low”, “middle” and“high” and denoted with different respective types of lines in thefigure). In this “same content” case, the transmission periodicity isdetermined according to the worst (e.g. 15 db CE) extension (cf. “P1” inthe figure). However, the terminals supporting other CE levels (5 dB, 10dB) may read (receive and store/attempt to decode) the SI lessfrequently as is illustrated by the arrows with different respectivetypes of line.

In order to save battery power at the wireless device, the wirelessdevices (UEs) with better reception quality (i.e. lower CE level)performed the reception of the common content less frequently than it istransmitted.

It is noted that the wireless terminal which successfully received theinformation after a number of repetitions lower than the maximum numberof repetitions may stop receiving the remaining repetitions.

Another strategy that these UEs could employ is to accumulate and softcombine receptions using all or most of the frequent transmissions andafter a successful reception just enter sleep mode. In other words, thewireless device tries to decode the system information after receptionof each repetition and as soon as the decoding succeeds, the receptionof further repetitions is stopped. This strategy provides the advantageof possibly faster acquisition of the system information. Fornon-Broadcast e.g. dedicated or unicast message(s) like Paging, the UEmay even inform the network upon stopping so that the network can stopthe further (re) transmissions of the dedicated or unicast message(s).In other words, the wireless device may further include a transmissionunit for transmitting to the network and notification of terminatedreception of the system information.

Concerning the term “repetition”, this term is not limited to bit-wiserepetition on the physical layer. On the contrary, the repetitions maybe different redundancy versions or, generally, different versions ofthe same system information content. The concept of retransmissions andcombining with HARQ has been described above in the background section.However, the principles of transmitting different redundancy version ofthe coded data may be extended to any repeated transmission schemewithout requiring any feedback from the receiver. In case of systeminformation, which is broadcasted to be received from a plurality ofterminals, no feedback schemes are used. However, instead of providingmere repetitions of the system information, it is beneficial to transmitdifferent redundancy versions in order to increase combining gain. Thus,also an exemplary embodiment of the present disclosure, combinable withany other embodiments of this disclosure, includes transmittingdifferent redundancy versions of encoded system information (i.e.different portions of the encoded system information) similarly to theretransmissions as described above for HARQ and as employed in thecurrent LTE/LTE-A standard. The combining may also work in the same way,for instance the incremental redundancy combining, possibly alongsidewith the soft combining of different repetitions of the redundancyversions transmitted).

In other words, in the “same content” case, there is only one content(SI/SIB) transmission but the receiving UEs receive the content withfrequency (corresponding to periodicity) based on their respectiveoperating CE level.

For example, UEs with configured 5 dB CE level will receive the commoncontent only 5 times in the given time period, on the other hand, UEswith configured 10 dB CE level will receive the common content twice asoften, i.e. 10 times in the given time period. Moreover, UEs withconfigured 15 dB CE level will further receive the common content moreoften, for instance twice as often as the 10 dB level UEs (i.e. 20 timesin this example).

The given period may correspond to the system information window or amultiple thereof, which is a time domain interval in which one systeminformation message (SI message as in legacy system described above) andtheir respective repetitions are conveyed.

In practice, having as many SIBs as CE levels may be difficult to acceptsince it represents a very different approach from legacy system wherethe grouping is mainly based on logical purpose/usability. Moreover,providing separate SIBs for all respective separate CE levels may add tocomplexity of scheduling and SI change notification given that thescheduler has to now take care of 4 times more SIB/SIs corresponding tothe four levels of CE. When an IE that has different value for each ofthe CE level changes then the Change Notification needs to be sent tothe concerned UEs. Since the concerned UEs need different CE supporteven to receive the SI Change Notification, this adds further burden onthe eNB scheduler.

Accordingly, it may be beneficial to keep the legacy system unaffectedby the updates of the MTC specific SIBs. A new, separate New Value Tagor Tags may thus be provided in order to signal to the wireless devicesthat the system information concerning MTC operation and in particularCE operation has changed. The new value Tag may be separate for the“Different Content” group and for the “Common Content” group. Moreover,the new value Tag may be specific and separate for each CE level or foreach CE level group (e.g. Groups A and B as described below). The typeof change may also be signaled within a paging message which istransmitted from the network to the wireless devices to notify them ofthe system information change. The type of change may indicate the CElevel for which the SI changed and/or whether the change concerns theIEs common for all CE level or the IEs specific for each level.

The modification period (smallest time period after which the SI maychange) may also be set differently and independently for the “CommonContent” and the “Different Content” system information. In addition,the change period may also be set differently for different respectiveCE levels or CE level groups.

It is noted that different SI/SIB may also be transmitted in aninterleaved manner as illustrated in FIG. 10. In particular, as can beseen from the three diagrams (a), (b), and (c), there are at least threeways to arrange the SI transmission with or without interleaving ofSI/SIB. In the first scheme (a), the maximum number of transmission fora SIB/SI is completed and then the transmission for the next one SIB/SIstarts. This is the scheme without interleaving.

In the second scheme (b), SIB/SIs are interleaved and a transmission ismade once in each 20 ms period. This scheme should further benefit fromthe time diversity and likely fewer transmissions than maximum number oftransmission for a SIB/SI in the first scheme would be required.

As the receiver behaviour, two schemes are possible. Scheme A is to havemore than one HARQ process (as many as the number of interleaved Sis—inthis example 2). Then, after one cycle of SI transmission period, UEcould receive multiple SIs simultaneously. Scheme B is the receiver hasonly one HARQ process and only to receive one SI during one SItransmission period. In order to receive “n” SIs, UE needs to receive“n” cycles of SI transmission periods.

This scheme B may be applied by the receiver irrespectively of whetherinterleaving is applied by the network.

In the third scheme (c), only the corresponding SIB/SI transmissions arespread by 20 ms; whereas the broadcasting is taking place every 10 ms(in 2 SIB/SI interleaving case).

In the table below a comparison is made among the three schemes.

TABLE 2 Advantages Disadvantages Scheme 1 Requires one HARQprocess/buffer in the MTC devices Could require some more transmissionsthan scheme 2A. FIG. 10 (a) Good from Broadcast Overhead perspective (5%= 1/20) Scheme 2 Best from Broadcast Overhead perspective (<5%) SchemeA: Requires more than one HARQ process FIG. 10 (b) (as many as thenumber of interleaved SIs) Scheme B: Longest time required to receivemultiple SIs. Scheme 3 Quickest total System Information acquisitionRequires more than one HARQ process FIG. 10 (c) (as many as the numberof interleaved SIs) Double the Broadcast Overhead perspective (10%)

Given the delay tolerant nature of the MTC application, the Schemes (a)and (b) seem to be advantageous. If Low Complexity/Cost discourages morethan 1 HARQ buffer for broadcasting, then Scheme (a) is advantageouswhich also maintains the legacy principle of non-overlapping SI-windows.However, from Coverage Extension perspective, Scheme (b) might be bettersuited. It is noted that the above example only shows interleaving of 2different SIBs (system information). However, in general, theinterleaving may be also performed for any other number of SIBs. Asmentioned above, the interleaving is similar to the concept of HARQprocesses even if in case of SIB/SI there are no retransmissions basedon feedback. However, the repetitions/versions of one SIB/SI may beconsidered as retransmissions of the same data.

Moreover, in general one particular SI may have one particularmodification boundary and another will have another particularmodification boundary and the two might overlap. Modification boundaryhere refers to the time point at until when the system information willnot change but only from the start of the next modification period.

In general, the transmission of a plurality, N (N>1 being integer) typesof system information may be interleaved which means that N differentsystem information (SIBs) are transmitted cyclically a predefined numberR of repetitions/versions (R being integer larger than 1). According toan embodiment, there are only two groupings of the same IEs for tworespective groups of EC levels. But the boundary of the two groupingscan be flexible, for instance as shown in the following.

1) a first grouping “Grouping-A” for zero CE level and a second grouping“Grouping-B” for low, medium, and high CE level2) a first grouping “Grouping-A” for zero and low CE level and a secondgrouping “Grouping-B” for medium and high CE level3) a first grouping “Grouping-A” for zero, low, and medium CE levels anda second grouping “Grouping-B” for high CE level4) only one grouping which is the same regardless of the CE level (zero,low, medium, high)

For instance, the applicability of the above configurations 1) to 4) maybe signaled within system information carried by SIB1 or a SIB carryingscheduling information (as will be exemplified below with reference toFIGS. 6 and 7).

Moreover, Grouping-A may be indicated by a separate SIBx-A (x denotingany SIB like SIB1 or SIB etc., e.g. SIB2-A means SIB2 for group A) andGrouping-B may be indicated by a separate SIBx-B different from SIBx-A.The number of the repetitions (and/or redundancy versions) can bedifferent between SIBx-A and SIBx-B. Advantageously, SIBx-A and SIBx-Bare carried in their respective separated SI messages (separately).Their scheduling may also be independent. Number of repetitions(versions) may also differ for SIBx-A and SIBx-B and depend on the CElevels included.

The SIB1 or the scheduling Information (wherever signaled) may alsoindicate further scheduling details of SIBx-A and SIBx-B, such asfrequency position (PRB start and/or end, subframe pattern or specifictime domain positions, frequency hopping flag etc.

It is noted that the above interleaving as shown in FIG. 10 may beapplied to the different groups as described above. FIG. 10 showsoverlapping of 2 different SIBs. These SIBs may be SIBx-A and SIBx-B asexemplified above, i.e. SIBs carrying different CE-level groupings.Alternatively or in addition, the interleaving (as shown by dashed andsolid lines in FIG. 10, schemes (b) and (c)) may be performed betweenthe “Common Content” SI and between CE level specific CEs.

The above example described with reference to FIG. 5 shows that theperiodicity with which the CE level specific information is transmittedmay also be specific for a CE level, i.e. different for at least twodifferent CE levels. In other words, the IEs specific for each CE levelmay be grouped for each respective CE level. For instance, one SIB mayinclude IEs from only one CE level. Alternatively in general, the IEsspecific for each CE level may be grouped for a plurality of CE levels.For instance, one SIB may include IEs from two or more CE levels. It isnoted that this can also be implemented by providing IEs with two ormore values for the respective two or more CE levels. Especially in casein which a plurality of CE levels are grouped and transmitted with thesame frequency, other receiving terminal may be configured to receivethe IEs with the frequency lower than the frequency with which these IEsare transmitted. This approach may help reducing the power consumptionat the terminal.

For instance, let us assume a case in which IEs of two CE levels (middleand high) are transmitted with a first periodicity corresponding to thehigh CE level so that the wireless devices applying the high CE levelare also able to receive this system information. Let us assume that awireless device is applying the middle CE level. This wireless devicedoes not necessarily need to receive all transmissions and in order tosave battery power it may be configured to receive the IEs lessfrequently than given by the first periodicity.

In the above example, it is assumed that there is a certain time periodin which the transmission of system information concerning the differentCE levels and including the repetitions is to be completed. Therefore,the certain time period corresponds to the maximum time in which theacquisition of the system information can be performed. The number ofrepetitions for different CE levels differs, which results in this caseinto different frequency of transmitting the IEs (SIBS) for different CElevels.

However, the present disclosure is not limited to this approach. Ingeneral, the number of repetitions may vary without the requirement ofkeeping them within the same time period. Thus, the periodicity(frequency) of transmitting system information corresponding todifferent CE levels may remain the same. This means that the maximumtime for acquisition of the system information for the CE levelcurrently applied would depend on that CE level.

In the following an exemplary operation of a system informationreceiving apparatus is described. This may be a wireless device such asa terminal (UE) of any form, for instance a mobile phone, smart phone,tablet, laptop, PC, wireless card, USB connectable receiver, or anyother device.

A wireless device supporting coverage enhancement may at first determineits CE level. The determining of the appropriate level may be performede.g. based on pathloss calculations and/or cell measurements or thelike. Then, the wireless device checks if the cell in which it islocated supports the determined CE level. This checking is performed byreceiving broadcast information including a CE level indication. The CElevel indication may be received, for instance in MIB or SIB1 or inanother SIB as discussed above. It could implicitly be signaled bylooking at the number of transmitted values (instances) of one of theparameters (out of many such possible candidates) as explained earlier.Based on the received CE level indication, the wireless devicedetermines if the required CE level is supported in the network. The UEmay determine the ‘required’ CE level by means of the time/effortrequired to detect a cell, or by the time/effort required to receive MIBor some other SIB or even the reception quality like RSRP (ReferenceSignal Received Power) or RSRQ (Reference Signal Received Quality) oreven using pathloss estimate (higher the pathloss, higher the requiredCE Level). Based on the CE level set, the wireless device determines itsinterest/need for SI acquisition i.e. whether “different content” typeor “same content” type is to be received and with which frequency. Thisdetermination may be based for instance on a behaviour defined inspecification and/or based on a scheduling information. In particular,the scheduling of the common SIBs and/or the CE level specific SIBs maybe defined by a scheduling information transmitted within systeminformation such as MIB or SIB1 or another SIB. Alternatively, thescheduling may obey certain rules defined in a specific case of standardand may require blind detection using a group RNTI such as an MTCspecific MTC-RNTI or general SI-RNTI for system information or EC-RNTIspecific for coverage enhancement or for a particular CE level.

Then, the wireless terminal acquires the corresponding schedulinginformation and thereafter the SI intended (desired and correspondingwith the own determined CE level), by waking up to receive SI onlyaccording to its schedulings (irrespective of transmission frequency).

The devices which do not support CE, may further operate as in thelegacy system (current LTE standard), i.e. operate normally in goodcoverage; or declare out of service in bad/extended/no coverage.

FIG. 6 illustrates an example of acquiring system information accordingto an embodiment. In particular, the network advertises the CE levelssupported in an implicit or explicit manner as described above, i.e. byincluding the CE levels explicitly into the information broadcasted inthe cell or by deriving the CE levels from other parameters broadcastedin the cell.

Then or before this step, the wireless device detects its current CElevel. This may be performed for instance based on pathloss calculation(and/or RSRP, Reference Signal Received Power, or Q measurements such asReference Signal Receive Quality, RSRQ).

Following are examples of conditions which may be used to the determinedthe current CE level by the wireless device:

1) if x<Pathloss then the CE level is the determined as high2) if y<Pathloss<x then the CE level is the determined as medium3) if z<Pathloss<y then the CE level is the determined as low

In the above conditions the following inequality applies x>y>z and theparameters x, y, and z are thresholds on pathloss which may bebroadcasted within system information, for instance in MTC SIB1 or inMIB or in another SIB. Alternatively, similar conditions may beformulated for RSRP or RSRQ or for any other measured variablereflecting channel conditions and the corresponding thresholds may beadvertised by the network or defined within the standard.

After determining its own CE level, if the determined CE level issupported by the network, the wireless (MTC) device acquires the“Different Content” and the “Common Content” system information for itsdetermined CE level, as illustrated in FIG. 6.

The reception of the system information related to the determined CElevel may be facilitated by receiving scheduling information which istransmitted by the network within the cell. In particular, thescheduling information may be broadcasted as a part of SIB 1. However,the present disclosure is not limited thereto and the schedulinginformation for system information concerning different CE levels mayalso be provided within a standalone system information block. In orderto keep the complexity low, such standalone system information block maybe directly scheduled from SIB1 (or MIB). However, these are onlyexamples and in general the system information for particular CE levelsmay be scheduled in another way, for instance in the MIB or in a systeminformation block for which blind detection is necessary.

FIG. 6 illustrates an exemplary grouping of the information elementspertaining to different CE levels. In particular, the common contentwhich is the same for all possible CE levels may include systeminformation messages SI-3 and SI-4. System information messages are (inthe LTE terminology) RRC protocol messages, of which each may includeone or more system information blocks as described above in thebackground section. In the present example, system information messageSI-3 includes two system information blocks, namely SIB-M and SIB-(M+1).On the other hand, system information message SI-4 includes two otherinformation blocks, namely SIB-(M+2) and SIB-(M+3). However, this ismerely an example and the structure of the common content may alsoinclude one single system information message carrying a single one or aplurality of system information blocks. System information blockstypically group elements with similar purpose (cf. background sectionabove).

The system information which is different for different CE levels (cf.“Different Content” in FIG. 6) is also exemplified in FIG. 6.Accordingly, there are two different system information messages SI-1and SI-2 for each of the four CE levels “zero”, “low”, “medium” and“high”. System information message SI-1 includes two system informationblocks, namely SIB-N and SIB-(N+1). In general, the system informationmessage may also include one single SIB or more than two SIBs. Thesystem information message SI-2 includes only one system informationblock denoted as SIB-(N+2) which is also merely exemplary. As can beseen from this example, system information for each of the different CElevels here has the same structure in terms of system informationmessages and system information blocks. Accordingly, the values of theinformation elements carried in the corresponding SIBs for different CElevels may be set independently, and thus may have different values. Theinformation elements which are common for all CE levels in this exampleare organized independently and differently from the “Different Content”system information. In particular, the “Common Content” includes systeminformation messages and also system information blocks different fromthose included in the “Different Content” system information.

However, it is noted that this is not meant to limit the presentdisclosure to such system information organization. Rather, someportions of the same SIB may be carried within the “Different Content”section whereas other portions of the same SIB may be carried within the“Common Content”.

The structure of the system information illustrated in FIG. 6 may existparallel to the system information to be read by a legacy wirelessdevice, to the system information specified by the current LTE standard.

FIG. 7 illustrates a comparison between the structure of systeminformation currently applied by LTE and the structure of systeminformation according to an advantages embodiment. On the left-hand sidethe legacy structure is shown. In particular, the most information block(MIB) is broadcasted on the physical broadcast channel. SIB1 schedulingis fixed in time domain and the UE performs blind decoding using SI-RNTIon these specific time instances (subframes) to find the frequencylocation of SIB 1. SIB1 then includes scheduling information for systeminformation messages SI-1, SI-2, SI-3 carrying further systeminformation blocks.

The SystemInformationBlockType1 (SIB1) uses a fixed schedule with aperiodicity of 80 ms and repetitions made within 80 ms. The firsttransmission of SystemInformationBlockType1 is scheduled in subframe #5of radio frames for which the SFN mod 8=0, and repetitions are scheduledin subframe #5 of all other radio frames for which SFN mod 2=0. A singleSI-RNTI is used to address SystemInformationBlockType1 as well as all SImessages.

The system information structure of the present embodiment which isparticularly suitable for MTC LC/EC mode is shown on the right-hand sideof FIG. 7. The MIB is the same as the MIB used for legacy system (on theleft hand side). However, some bits which were reserved in the MIB asspecified in the current LTE standard are used here to carry informationabout the location (within the resource grid), periodicity, frequencyhopping, and/or TBS (Transport Block size) etc. of a SIB1. In thisexample, the SIB1 (MTC-SIB1) is specific for the MTC LC/EC and differsfrom the legacy SIB1 (in general, resources for SIB1). The MTC-SIB1 inthis example further refers to a separate SIB including schedulinginformation for Ms common for different CE levels and schedulinginformation for SIBs different for different CE levels. In particular,the scheduling information indicates location of system informationmessage SI-2 and system information message SI-3. System informationmessage SI-1 may be directly referred to from the MTC-SIB 1.

However, the present disclosure is not limited to this example. Forinstance, SIB1 of the legacy system may also be reused instead ofproviding a separate MTC specific SIB 1. Moreover, SIB1 (legacy or MTCspecific) may also point only to the scheduling information and not toother system information messages/blocks. The scheduling informationwould then carry all information concerning to scheduling of systeminformation for different CE levels. In the example above the schedulinginformation is a part of a separate system information block. However,the system information block may also include further informationconcerning the MTC and/or different CE levels. For instance, it mayinclude the system information common for all CE levels andsystemInfoValueTag for the whole System information separately for eachCE level or even many-systemInfoValueTag(s), one for eachfunctionality/procedure/SIB etc. for each CE level or for all CE levelsgrouped together.

Alternatively, the scheduling information may be included directly inthe SIB1 (or MTC-SIB1).

The above disclosed embodiments and examples may provide variousbenefits. For instance, the cell support for any particular CE level isvisible to a wireless device and the wireless device can also calculateits own required coverage extension. Moreover, the cell/system load isrestricted to a reasonable limit with the above described structuring(grouping) of system information related to coverage enhancement. TheeNB scheduler (in general the scheduler of the network node transmittingthe system information) implementation and/or behavior is notcomplicated. Moreover, the legacy UEs (wireless devices which do notsupport coverage enhancement such as LTE and LTE-A devices supportingreleases 8 to release 13) are not affected. The MTC device behavior inacquiring, re-acquiring upon change of levels and upon SI changenotifications is clear.

The present disclosure provides an apparatus 800A for receiving systeminformation in a wireless communication system supporting coverageenhancement as shown in FIG. 8.

This apparatus may be any wireless apparatus such as a user device(terminal) of any type such as mobile phone, smart phone, tablet,computer, computer card or USB connectable wireless interface, or thelike.

The apparatus advantageously includes an SI receiving unit 820 thatreceives system information; and an SI control unit 810 that controlsthe SI receiving unit 820 to receive system information including acoverage enhancement level indication for indicating enhanced coveragelevels supported by the wireless communication system, and to receivesystem information including a group of information elements common fordifferent coverage enhancement levels and one or more groups ofinformation elements specific for different coverage enhancement levels.

The grouping of the CE-level-specific information may be performed forthe respective CE levels (or groups of CE levels). For instance, thegrouping here may be performed on a system information block basis, suchthat a separate SIB is provided for each CE level (or for a subset of CElevels) and another separate SIB is performed for the IEs common to allCE levels. Alternatively, the grouping may be performed on aninformation element basis, i.e. each IE includes respective values forthe corresponding CE levels. Other groupings are also possible,including mixing of the above SIB-based and IE-based approach.

For instance, the system information is transmitted in systeminformation blocks; and the group of information elements common fordifferent coverage enhancement levels is transmitted in a systeminformation block different from the system information block in whichthe information elements specific for at least one different coverageenhancement level are transmitted.

The information elements for a first coverage enhancement level arereceived in a number of repetitions higher than the number ofrepetitions with which information elements for a second coverageenhancement level are received, wherein the first coverage enhancementlevel is higher than the second coverage enhancement level.

This arrangement ensures that the terminals having worse channelconditions (corresponding to higher CE level) may receive more SIrepetitions in order to increase the probability of correct SIacquisition (correct decoding).

According to an embodiment, the group of information elements common fordifferent coverage enhancement levels is transmitted with a firstfrequency, and the SI control unit 810 is configured to control the SIreceiving unit 820 to receive versions of the group of informationelements common for different coverage enhancement levels with afrequency equal to or lower than the first frequency, depending on thecoverage enhancement level currently applied by the apparatus.

Thus, the terminals applying different coverage enhancement levels mayread the SI with different frequency and thus, improve the tradeoffbetween battery power and speed of SI acquisition time. However, thepresent disclosure is not limited to this arrangement. Rather, eachterminal may read all repetitions (versions) of SI and stop thereception as soon as the SI was decoded successfully. Otherimplementations are possible, for instance, the wireless devices ofdifferent CE levels may be configured to receive only certain number ofthe repetitions (versions).

The coverage enhancement level indication received may include at leastone of:

-   -   a list of supported coverage enhancement levels,    -   the highest supported coverage enhancement level, wherein the        apparatus is configured to derive the supported coverage        enhancement levels as all levels smaller than or equal to the        received highest supported coverage enhancement level,    -   a number of values of a particular information element, wherein        the apparatus is configured to derive the supported coverage        enhancement levels according to the number of the values of the        particular information element, and    -   a single value of an information element, wherein the apparatus        is configured to derive the supported coverage enhancement        levels according to the single value of the information element.

Accordingly, the coverage enhancement levels supported by the networkmay be advertised either explicitly by broadcasting the correspondingsystem information in a MIB, SIB1 or other SIB) or implicitly byindicating the CE levels supported for instance by means of the numberof values of a particular information element(s) or even by indicatingthe periodicity of M-SIB1 (higher periodicity of M-SIB1 means highest CElevel supported; medium periodicity of M-SIB1 means medium CE levelsupported and so on) or even by associating e.g. the possible startingpositions of MSIB1 to particular levels of CE support (starting position[say PRB index] of M-SIB1=X would mean CE level support high; startingposition [PRB index] of M-SIB1=Y would mean CE level support medium; andso on). As an example for periodicity, say CE level high, med, low has20, 60 and 100 as periodicity. Then when MIB indicates periodicity as20, a UE knows that periodicities 60 and 100 are also supported i.e. CElevels med and low are also supported when CE level high is supported.

Thus, concerning the indication by a single value of an informationelement, this may be, for an information element indicating periodicity(frequency of occurrence). For instance, CE level high, medium, and lowmay have 20, 60 and 100 ms as periodicity. Then when MIB indicatesperiodicity as 20, a UE knows that periodicities 60 and 100 are alsosupported i.e. CE levels medium and low are also supported when CE level“high” is supported.

In particular, the SI control unit 810 may control the SI receiving unit820 to receive the system information in a plurality of versions.

Here, the term versions may denote redundancy versions or any other kindof content repetitions. For instance, the SI may be encoded by a forwarderror coding which adds redundancy. Examples of such coding may be theTurbo codes or convolutional codes as applied by the LTE. However, anyother coding is also possible such as block codes like LDPC, BCH or thelike. One version of such coded SI then corresponds to a portion of thecoded SI. Different portions—versions—of the coded SI may be transmittedat different times (for instance in different subframes). These portionsmay be individually decodable.

However, the SI versions may also be simple repetitions or a combinationof redundancy versions and their repetitions. For instance, there may befour (in general K, K being an integer larger than 1) redundancyversions defined for each SI message and these four RVs are transmittedcyclically repeated a plurality of times (in general N, N being aninteger larger than 1). The SI versions may be mapped to the respectivesubframes.

The apparatus may further include a combining unit that combines theplurality of versions received and a decoding unit that checks whetherthe system information after combining can be correctly decoded; and theSI control unit 810 is configured to prevent the SI receiving unit 820from receiving further versions of the system information if the systeminformation after combining can be correctly decoded.

The combining unit may include, for instance, a soft combiner whichcombines the detected bit reliabilities of the receivedversions/repetitions or a hard combiner which combines the detectedbits. The combining may include incremental redundancy combining ofdifferent redundancy versions to one coded block which is then decoded.

Moreover, the combining unit advantageously combines the plurality ofversions of system information received so far after reception of eachversion, and the decoding unit checks whether the system information canbe correctly decoded after each combining.

After receipt of each new SI version, the combining may be performed anda decoding may be attempted. However, the newly received SI version mayalso be attempted to decode individually at first and only combined ifit is not decodable correctly. The correctness of the decoding may bechecked by means of checking the cyclic redundancy check (CRC) attachedto the SI. However, other implementations are also possible withoutlimiting the present disclosure. For instance, the decoding may beattempted not after receiving each new SI version but rather afterreceiving (and possibly combining) each M (M being an integer largerthan 1) SI versions in order to reduce computational complexity.

According to an embodiment, the apparatus further includes a coverageenhancement level determining unit that determines own coverageenhancement level based on one of pathloss, Reference Signal ReceivedPower, and measurements such as Reference Signal Receive Quality andthat checks whether the determined own coverage enhancement level issupported by the wireless communication system based on the receivedcoverage enhancement level indicator, wherein, if the own coverageenhancement level is supported by the wireless communication system, theSI control unit 810 controls the SI receiving unit 820 to receive systeminformation for the own coverage enhancement level.

If the own coverage enhancement level is not supported by the currentnetwork cell, then the terminal may try to change the cell (by means ofCell reselection) or be out of the network coverage. However, otherbehavior may also be defined.

The SI control unit 810 may control the SI receiving unit 820 to receivescheduling information within a system information block referred tofrom a system information block (SIB1) of which the location isindicated in a master information block (MIB), and to receive systeminformation for the own coverage enhancement level according to thescheduling information.

This is only an advantageous example of scheduling the SIBs in which theSI concerning the CE is conveyed. In general, the scheduling may beperformed differently, for instance by directly referring to thescheduling information from the MIB or by in any other way. Thescheduling information may fully specify the resources on which the CElevel common and the CE level specific SI is transmitted. This has theadvantage of simplicity for the terminal implementation which merelyreceives the SI on the resources specified in the schedulinginformation. However, the complete scheduling information (includingtime and frequency domain resources, frequency hopping, transport blocksize (TBS) and modulation and coding scheme (MCS) etc.) also mayintroduce considerable signaling overhead. Alternatively, the schedulinginformation may only include a subset of resource specification whileother resource features are fixed. For instance, the frequency locationof the SI may be fixed to the central 6 PRBs or to any other subset offrequency resources. Alternatively or in addition, the application offrequency hopping may be fixed or signaled in other, less frequentmanner (in other SI) and the TBS and/or MCS may be fixed or signaledelsewhere. The time domain scheduling may include (or consist of) thespecification of subframes in which the SI is to be carried. Thescheduling information advantageously includes separate scheduling forthe separate groupings of IEs—the CE level independent group (IEs commonto all CE levels) and for the particular respective groupings specificto one or more CE levels.

For example, the coverage enhancement level indication may indicate oneor more of four different coverage enhancement levels, including a zerolevel indicating no coverage enhancement.

However, the number four is only exemplary and may be beneficial as itrequires only 2 bits of signaling and still provides distinguishing ofthree CE levels and no CE.

The system information for different coverage enhancement levels isgrouped according to one of the following configurations:

-   -   a first group for the zero level and a second group for the        remaining three coverage enhancement levels;    -   a first group for the zero level and the lowest of the four        coverage enhancement levels and a second group for the remaining        two coverage enhancement levels;    -   a first group for the zero level and the two lower enhancement        coverage levels and a second group for the highest of the four        coverage enhancement levels; and    -   one single group for all four coverage enhancement levels, and        the SI control unit 810 controls the SI receiving unit 820 to        receive the configuration currently used by the network within        system information.

It is noted that the above examples have shown four CE levels, alsoincluding the zero level. However, it is noted that the zero level doesnot have to be included as a separate CE level. For instance the generalusage of EC may be signaled or indicated implicitly in another place.

However, the zero level may mean that MTC is applied but without EC, forinstance only LC mode.

The system information may be MIB, SIB1, scheduling information SIB orany other SIB in general, as described above.

The configuration may be received within a system information messagefurther including a grouping of scheduling information indicating thelocation of a first system information block in which the first group iscarried and the location of a second system information block in whichthe second group is carried, the first system information block and thesecond system information block being mutually different.

For example, the wireless communication system is 3GPP Long TermEvolution, LTE, or LTE advanced, LTE-A, and the system informationmessages including system information blocks for enhanced coveragesupport except for master information block are received independentlyof the system information for LTE or LTE-A without supporting coverageenhancement.

Moreover, the present disclosure provides an apparatus 800B as shown inFIG. 8 for transmitting system information in a wireless communicationsystem supporting coverage enhancement.

The apparatus 800B may be, for instance a network node controlling thetransmission of system information within a cell. In particular, thenetwork node may be a base station such as a NodeB/eNodeB in UMTS andLTE (LTE-A) respectively. However, the present disclosure is not limitedthereto and any other device such as relay or any node in a wirelessnetwork transmitting system information may embody the apparatus 800B.

The apparatus 800B may include an SI transmitting unit 870 thattransmits system information; an SI control unit 860 that controls theSI transmitting unit 870 to transmit system information including acoverage enhancement level indication for indicating enhanced coveragelevels supported by the wireless communication system, and to transmitsystem information including a group of information elements common fordifferent coverage enhancement levels and information elements specificfor different coverage enhancement levels grouped for respectivecoverage enhancement levels.

In particular, as shown in FIG. 8, the apparatus 800B may be configuredto generate and transmit the system information which is scheduled,grouped, and/or structured as described above in connection withreception of the system information.

The methods for receiving and transmitting the system information areillustrated in FIG. 9. Accordingly, the present disclosure provides amethod 900A for receiving system information in a wireless communicationsystem supporting coverage enhancement including the steps of: receiving930 system information including a coverage enhancement level indicationfor indicating enhanced coverage levels supported by the wirelesscommunication system; and receiving 980 system information including agroup of information elements common for different coverage enhancementlevels and information elements specific for different coverageenhancement levels grouped for respective coverage enhancement levels.

The method 900A may also include further steps already described aboveperformed by various units of the corresponding receiving device. Inparticular, FIG. 9 shows step 910 of determining the own CE level (CEL)by the wireless device. The determining of the CE level may be performedbased on the measured channel quality as exemplary described above.Then, the wireless device receives 930 CE levels supported by thenetwork and in particular by the cell in which the wireless device islocated (connected to). It is noted that the steps and 910 and 930 canalso be executed in a reverse order. The wireless device then compares940 the determined own CE level and the CE levels supported by thenetwork in order to determine whether its own CE level is supported bythe network. In case the own determine CE level is not supported by thenetwork, the wireless device is out of coverage of the current cell forwhich the system information was analyzed. If the own CE level issupported by the network, in step 960 the wireless device receivessystem information scheduling information which indicates resources onwhich the system information concerning different CE levels istransmitted. Based on the scheduling information, in step 980 thewireless terminal receives system information concerning the owndetermined CE level. The transmission and reception of the systeminformation is performed over the wireless interface 990.

Furthermore, the present disclosure provides a method 900B fortransmitting system information in a wireless communication systemsupporting coverage enhancement including the steps of: transmitting 920system information including a coverage enhancement level indication forindicating enhanced coverage levels supported by the wirelesscommunication system; and transmitting 960 system information includinga group of information elements common for different coverageenhancement levels and information elements specific for differentcoverage enhancement levels grouped for respective coverage enhancementlevels.

This method is also exemplified in FIG. 9. Basically, the network nodetransmitting the system information performs the step 920 ofbroadcasting the CE level indication. Various possibilities offormatting the CE level indication are already described above withreference to the corresponding receiving apparatus. The network nodealso advantageously transmits 950 scheduling information specifying onwhich resources the system information concerning specific CE levels istransmitted. Finally, the system information concerning specific CElevels is transmitted in step 960. The scheduling and formatting as wellas grouping of the system information and the related the data(scheduling information and the like) is also described above in variousexamples and embodiments.

In another general aspect, the techniques disclosed here feature anapparatus for transmitting system information in a wirelesscommunication system supporting coverage enhancement comprising: atransmission unit for transmitting system information; a control unitfor controlling the transmitting unit to transmit system informationincluding a coverage enhancement level indication for indicatingenhanced coverage levels supported by the wireless communication system;and to transmit system information including a group of informationelements common for different coverage enhancement levels andinformation elements specific for different coverage enhancement levelsgrouped for respective coverage enhancement levels.

In another general aspect, the techniques disclosed here feature amethod for receiving system information in a wireless communicationsystem supporting coverage enhancement comprising the steps of:receiving system information including a coverage enhancement levelindication for indicating enhanced coverage levels supported by thewireless communication system; and receiving system informationincluding a group of information elements common for different coverageenhancement levels and information elements specific for differentcoverage enhancement levels grouped for respective coverage enhancementlevels.

In one general aspect, the techniques disclosed here feature a methodfor transmitting system information in a wireless communication systemsupporting coverage enhancement comprising: transmitting systeminformation including a coverage enhancement level indication forindicating enhanced coverage levels supported by the wirelesscommunication system; and transmitting system information including agroup of information elements common for different coverage enhancementlevels and information elements specific for different coverageenhancement levels grouped for respective coverage enhancement levels.

In accordance with another embodiment, a non-transitorycomputer-readable recording medium storing a computer-readable programcode embodied thereon is provided, the program code being adapted tocarry out the present disclosure.

Other exemplary embodiments relate to the implementation of the abovedescribed various embodiments using hardware and software. In thisconnection a user terminal (mobile terminal) and an eNodeB (basestation) are provided. The user terminal and base station is adapted toperform the methods described herein, including corresponding entitiesto participate appropriately in the methods, such as receiver,transmitter, processors.

It is further recognized that the various embodiments may be implementedor performed using computing devices (processors). A computing device orprocessor may for example be general purpose processors, digital signalprocessors (DSP), application specific integrated circuits (ASIC), fieldprogrammable gate arrays (FPGA) or other programmable logic devices,etc. They may include a data input and output coupled thereto. Thevarious embodiments may also be performed or embodied by a combinationof these devices.

Further, the various embodiments may also be implemented by means ofsoftware modules, which are executed by a processor or directly inhardware. Also a combination of software modules and a hardwareimplementation may be possible. The software modules may be stored onany kind of computer readable storage media, for example RAM, EPROM,EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc.

It should be further noted that the individual features of the differentembodiments may individually or in arbitrary combination be subjectmatter to another embodiment.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present disclosure asshown in the specific embodiments. The present embodiments are,therefore, to be considered in all respects to be illustrative and notrestrictive.

Summarizing, The present disclosure relates to transmitting andreceiving of system information which includes controlling thetransmission and/or the reception to transmit and/or receive systeminformation including a coverage enhancement level indication forindicating enhanced coverage levels supported by the wirelesscommunication system and to transmit and/or receive system informationincluding a group of information elements common for different coverageenhancement levels and information elements specific for differentcoverage enhancement levels grouped for respective coverage enhancementlevels.

What is claimed is:
 1. An integrated circuit for controlling acommunication apparatus, the integrated circuit comprising: receivingcircuitry, which, in operation, receives system information for thecommunication apparatus in Coverage Enhancement (CE), the systeminformation including information elements common to a plurality of CElevels including one or more radio condition threshold values used todetermine a CE level out of the plurality of CE levels and at least oneinformation element specific to one or more of the plurality of CElevels; control circuitry, which, in operation, performs soft-combiningof the received system information in a plurality of redundancy versionscyclically repeated a defined plurality of times; and decodingcircuitry, which, after each of the soft-combining, attempts to decodethe system information, wherein the receiving circuitry, in operation,receives the information elements common to the plurality of CE levelswith a second frequency equal to or lower than a first frequency withwhich the information elements common to the plurality of CE levels aretransmitted, depending on a current CE status of the communicationapparatus.
 2. The integrated circuit according to claim 1, wherein thereceiving circuitry, in operation, receives the system information insystem information blocks, and a system information block in which theinformation elements common to the plurality of CE levels are receivedis different from a system information block in which the at least oneinformation element specific to one or more of the plurality of CElevels is received.
 3. The integrated circuit according to claim 1,wherein the received one or more radio condition threshold valuescomprise at least one of: a list of supported CE levels, a highestsupported CE level, wherein the supported CE levels are all levelssmaller than or equal to the highest supported CE level, a number ofvalues of an information element, and a single value of an informationelement, wherein the supported CE levels are derived from the number ofvalues of the information element or from the single value of theinformation element.
 4. The integrated circuit according claim 1,comprising: coverage enhancement level determination circuitry, which,in operation, determines the CE level based on at least one of pathloss,Reference Signal Received Power (RSRP), and measurements includingReference Signal Receive Quality (RSRQ), and checks whether thedetermined CE level is supported by a network based on a CE levelindication included in the received one or more radio conditionthreshold values.
 5. The integrated circuit according to claim 1,wherein the receiving circuitry, in operation, receives schedulinginformation within a system information block 1 (SIB1), of which alocation is indicated in a master information block (MIB), and receivesthe system information according to the scheduling information.
 6. Theintegrated circuit according to claim 1, wherein a CE level indicationincluded in the received one or more radio condition threshold valuesindicates one or more of four different CE levels, including a zerolevel indicating no CE, the system information for the four CE levels isgrouped according to one of the following configurations: a first groupfor the zero level and a second group for the remaining three CE levels;a first group for the zero level and the lowest of the four CE levelsand a second group for the remaining two CE levels; a first group forthe zero level and two lower CE levels and a second group for thehighest of the four CE levels; and one single group for all of the fourCE levels, and the receiving circuitry, in operation, receives theconfiguration currently used by a network within the system information.7. The c integrated circuit according to claim 6, wherein the receivingcircuitry, in operation, receives the configuration within a systeminformation message, the system information message including schedulinginformation indicating a location of a first system information block,in which the first group is carried, and a location of a second systeminformation block, in which the second group is carried, the firstsystem information block and the second system information block beingmutually different.
 8. The integrated circuit according to claim 1,wherein the receiving circuitry, in operation, receives the systeminformation which supports CE, independently of second systeminformation which does not support CE.
 9. A communication apparatus,comprising: a receiver, which, in operation, receives system informationfor the communication apparatus in Coverage Enhancement (CE), the systeminformation including information elements common to a plurality of CElevels including one or more radio condition threshold values used todetermine a CE level out of the plurality of CE levels and at least oneinformation element specific to one or more of the plurality of CElevels; control circuitry, which, in operation, performs soft-combiningof the received system information in a plurality of redundancy versionscyclically repeated a defined plurality of times; and a decoder, which,after each of the soft-combining, attempts to decode the systeminformation, wherein the receiver, in operation, receives theinformation elements common to the plurality of CE levels with a secondfrequency equal to or lower than a first frequency with which theinformation elements common to the plurality of CE levels aretransmitted, depending on a current CE status of the communicationapparatus.
 10. The communication apparatus according to claim 9, whereinthe receiver, in operation, receives the system information in systeminformation blocks, and a system information block in which theinformation elements common to the plurality of CE levels are receivedis different from a system information block in which the at least oneinformation element specific to one or more of the plurality of CElevels is received.
 11. The communication apparatus according to claim9, wherein the received one or more radio condition threshold valuescomprise at least one of: a list of supported CE levels, a highestsupported CE level, wherein the supported CE levels are all levelssmaller than or equal to the highest supported CE level, a number ofvalues of an information element, and a single value of an informationelement, wherein the supported CE levels are derived from the number ofvalues of the information element or from the single value of theinformation element.
 12. The communication apparatus according claim 9,comprising: coverage enhancement level determination circuitry, which,in operation, determines the CE level based on at least one of pathloss,Reference Signal Received Power (RSRP), and measurements includingReference Signal Receive Quality (RSRQ), and checks whether thedetermined CE level is supported by a network based on a CE levelindication included in the received one or more radio conditionthreshold values.
 13. The communication apparatus according to claim 9,wherein the receiver, in operation, receives scheduling informationwithin a system information block 1 (SIB1), of which a location isindicated in a master information block (MIB), and receives the systeminformation according to the scheduling information.
 14. Thecommunication apparatus according to claim 9, wherein a CE levelindication included in the received one or more radio conditionthreshold values indicates one or more of four different CE levels,including a zero level indicating no CE, the system information for thefour CE levels is grouped according to one of the followingconfigurations: a first group for the zero level and a second group forthe remaining three CE levels; a first group for the zero level and thelowest of the four CE levels and a second group for the remaining two CElevels; a first group for the zero level and two lower CE levels and asecond group for the highest of the four CE levels; and one single groupfor all of the four CE levels, and the receiver, in operation, receivesthe configuration currently used by a network within the systeminformation.
 15. The communication apparatus according to claim 14,wherein the receiver, in operation, receives the configuration within asystem information message, the system information message includingscheduling information indicating a location of a first systeminformation block, in which the first group is carried, and a locationof a second system information block, in which the second group iscarried, the first system information block and the second systeminformation block being mutually different.
 16. The communicationapparatus according to claim 9, wherein the receiver, in operation,receives the system information which supports CE, independently ofsecond system information which does not support CE.